The standard argument deploring judicial activism is that all too often interested parties who have failed to achieve their political objectives through the legislative process or by petitioning administrative or regulatory agencies turn to the courts to try to get what they have failed to get through the political process.

This argument is not always applicable to Supreme Court decisions that are criticized. A key function of the court in the divided government the U.S. Constitution created is precisely to determine whether actions taken by the legislative or executive branches are constitutional. If the court determines that they are not constitutional, it is not engaging in judicial activism when it invalidates a law or administrative action; it is doing its job.

Unfortunately, in Massachusetts et. al. v. Environmental Protection Agency et. al. a Supreme Court divided 5-4 engaged in precisely the kind of judicial activism that people on all sides of the ideological spectrum correctly deplore. In short, the popular passions around global warming carried the day, rather than calm legal precedent and thought.

The Clean Air Act of 1970, as amended most recently in 1990, says that the EPA administrator “shall by regulation prescribe (and from time to time revise) … standards applicable to the emission of any air pollutant … which in his judgment cause, or contribute to, air pollution” coming from new cars. Despite the trendiness of concern about global warming, the EPA has so far declined to regulate carbon dioxide, a “greenhouse gas” coming from automobile tailpipes. Its reasons have not been trivial. The science on how much human-produced greenhouse gases contribute to global warming is unsettled, and U.S. motor vehicle emissions contribute about 6 percent of global carbon dioxide, and new cars contribute only a fraction of that.

So the EPA administrator, “in his judgment,” has decided that setting standards for new-car CO2 emissions is neither required by law nor a policy likely to help much. The fact that despite persistent lobbying Congress has not passed legislation mandating regulation of CO2 and other greenhouse gases, nor has the Senate approved the Kyoto treaty, provide some underpinning for this judgment.

Several private parties sued the EPA, asking the courts to force it to interpret the rather vague language in the Clean Air Act to define carbon dioxide as a pollutant that requires regulation. The case didn’t pick up steam until Massachusetts and several other states joined it, and thereby hangs another objection to the court’s decision.

Courts normally require “standing” to consider a lawsuit, meaning plaintiffs must allege a specific damage traceable to the defendant’s unlawful action or failure to act. The damage caused by the EPA’s failure to enact onerous mandates is tenuous at best, and the evidence that mandates would fix global warming is even more tenuous. But in his majority opinion, Justice John Paul Stevens said that as a sovereign state, Massachusetts is “entitled to special solicitude in our standing analysis.”

Giving special privileges to governments as compared to private parties is a particularly pernicious aspect of this case. We hope it doesn’t stand as a precedent.

Massachusetts v. EPA is a classic example of overreaching judicial activism. It opens the door for the EPA to consider CO2 emission regulations for automakers and other emitters, in an area where the passion is deeper than the science. It is likely to make life more expensive for everybody who drives or depends on trucks and other vehicles to get the goods and services they want close to home, without doing anything substantive about global warming.